Habitat and ecology: Widely distributed in the Chicago Region but not abundant as a weed. Often found in disturbed areas where competition has been reduced, such as where logging or fire has recently occurred.

All specimens from America identified as C. hybridum L. should be referred to this species. Its more or less smooth seed with its relatively easily detachable perianth separates it clearly from the European plant. It occurs in sandy fallow fields, and open or moist woods.